NAME

       aio_write — asynchronous write to a file (REALTIME)

LIBRARY

       Standard C Library (libc, -lc)

SYNOPSIS

       #include <aio.h>

       int
       aio_write(struct aiocb *iocb);

DESCRIPTION

       The  aio_write() system call allows the calling process to write iocb->aio_nbytes from the buffer pointed
       to by iocb->aio_buf to the descriptor iocb->aio_fildes.  The call returns  immediately  after  the  write
       request has been enqueued to the descriptor; the write may or may not have completed at the time the call
       returns.   If  the  request  could  not be enqueued, generally due to invalid arguments, the call returns
       without having enqueued the request.

       If O_APPEND is set for iocb->aio_fildes, aio_write() operations append to the file in the same  order  as
       the  calls  were made.  If O_APPEND is not set for the file descriptor, the write operation will occur at
       the absolute position from the beginning of the file plus iocb->aio_offset.

       If _POSIX_PRIORITIZED_IO is defined, and the descriptor supports  it,  then  the  enqueued  operation  is
       submitted at a priority equal to that of the calling process minus iocb->aio_reqprio.

       The  iocb  pointer  may  be  subsequently used as an argument to aio_return() and aio_error() in order to
       determine return or error status for the enqueued operation while it is in progress.

       If the request is successfully enqueued, the value of iocb->aio_offset can be modified during the request
       as context, so this value must not be referenced after the request is enqueued.

       The iocb->aio_sigevent structure can be used to request notification of  the  operation's  completion  as
       described in aio(4).

RESTRICTIONS

       The  Asynchronous  I/O  Control  Block structure pointed to by iocb and the buffer that the iocb->aio_buf
       member of that structure references must remain valid until the operation has completed.

       The asynchronous I/O control buffer iocb should be zeroed before the aio_write()  system  call  to  avoid
       passing bogus context information to the kernel.

       Modifications  of  the  Asynchronous  I/O  Control Block structure or the buffer contents are not allowed
       while the request is queued.

       If the file offset in iocb->aio_offset is past the offset  maximum  for  iocb->aio_fildes,  no  I/O  will
       occur.

RETURN VALUES

       The  aio_write()  function  returns the value 0 if successful; otherwise the value -1 is returned and the
       global variable errno is set to indicate the error.

ERRORS

       The aio_write() system call will fail if:

       [EAGAIN]           The request was not queued because of system resource limitations.

       [EINVAL]           The asynchronous notification method in iocb->aio_sigevent.sigev_notify is invalid  or
                          not supported.

       [EOPNOTSUPP]       Asynchronous  write  operations on the file descriptor iocb->aio_fildes are unsafe and
                          unsafe asynchronous I/O operations are disabled.

       The following conditions may be synchronously detected when the  aio_write()  system  call  is  made,  or
       asynchronously,  at  any  time thereafter.  If they are detected at call time, aio_write() returns -1 and
       sets errno appropriately; otherwise the aio_return() system call must be called, and will return -1,  and
       aio_error() must be called to determine the actual value that would have been returned in errno.

       [EBADF]            The iocb->aio_fildes argument is invalid, or is not opened for writing.

       [EINVAL]           The  offset iocb->aio_offset is not valid, the priority specified by iocb->aio_reqprio
                          is not a valid priority, or the number of bytes specified by iocb->aio_nbytes  is  not
                          valid.

       If the request is successfully enqueued, but subsequently canceled or an error occurs, the value returned
       by  the  aio_return()  system  call  is  per  the  write(2)  system  call,  and the value returned by the
       aio_error() system call is either one of the error returns from the write(2) system call, or one of:

       [EBADF]            The iocb->aio_fildes argument is invalid for writing.

       [ECANCELED]        The request was explicitly canceled via a call to aio_cancel().

       [EINVAL]           The offset iocb->aio_offset would be invalid.

SEE ALSO

       aio_cancel(2), aio_error(2), aio_return(2), aio_suspend(2), aio_waitcomplete(2), sigevent(3), siginfo(3),
       aio(4)

STANDARDS

       The aio_write() system call is expected to conform to the IEEE Std 1003.1 (“POSIX.1”) standard.

HISTORY

       The aio_write() system call first appeared in FreeBSD 3.0.

AUTHORS

       This manual page was written by Wes Peters <wes@softweyr.com>.

BUGS

       Invalid information in iocb->_aiocb_private may confuse the kernel.

Debian                                           August 19, 2016                                    AIO_WRITE(2)